1. Field of the Invention
The present invention relates to devices for removing obstructions from blood vessels.
2. Prior Art
The closing of blood vessels poses serious circulatory problems. A closure is generally referred to as a stenosis. Stenoses can result from many various types of tissue growth. Some stenoses may be calcified. Others consist of fibrous tissue. A great variety of events can cause stenoses and the resulting tissue can be of many forms.
A stenosis can prevent adequate blood flow to downstream parts of the body. An example of paramount importance is a stenosis in a coronary artery which provides blood to the heart muscle. Lack of blood to this muscle can cause an infarction or other heart problems.
Many methods have been tried to overcome this problem. Traditionally, surgery was performed to add bypass path around the obstruction. Balloon angioplasty was later developed to partially open occlusions without open heart surgery.
Another technique is to cut away the occluding tissue, rather than bypassing it or working around it. This is sometimes known as atherectomy.
A variety of atherectomy devices have been proposed. One example is the cutting device disclosed in U.S. Pat. No. 4,653,496 to Bundy et al issued Mar. 31, 1987. This device includes a helical hollow cutting tool with a sharpened edge which slices a stenosis. A cutting cannula also assists in cutting the stenosis.
Other devices, such as disclosed in the various Nash and Kensey patents, attempt to pulverize the stenosis. One example, U.S. Pat. No. 4,686,982 to Nash has a rotating cutting head which whips water at the stenosis. The combination of the cutting head and swiftly propelled water is claimed to demolish the stenosis into particles sufficiently small that they can safely flow through the bloodstream.
Of course, it is important that dangerous particles do not escape into the bloodstream during the atherectomy process. What is needed is a device that both safely cuts the stenosis and removes it from the bloodstream so that normal flow is restored and no dangerous particles escape.
The present invention is designed to improve on the prior art in that it engages a portion of the stenosis and holds it while the stenosis is cut. The cut portion of the stenosis is trapped within the device which can be withdrawn from the vessel to minimize the chance of any loose particles endangering the patient.